1. Field of the Invention
The present invention relates to a structure for reflection of light, and more particularly, to a structure for obtaining a light beam with a smaller converging angle and spot size.
2. Description of the Related Art
Please refer to FIG. 1, a partially cross sectional view of a conventional structure 100 for reflection of light is illustrated.
As shown in FIG. 1, the structure 100 comprises a reflector 101 for reflecting light, wherein a focus of the reflector 101 is represented by a point 102. The reflector 101 is generally an ellipsoid or a paraboloid. It should be understood for person skilled in the art that the light emitted from light source 103 which is not a perfect point light source and is inherently formed with an arc gap and located on the point 102 can be reflected by the ellipsoid and thus condensed on the other focus 104 of the ellipsoid, wherein a converging angle and a diameter of a spot size are denoted by xcex8 and "PHgr"d, respectively.
When the above-mentioned structure 100 is applied to a digital projector, in order to improve the illumination efficiency of the digital projector, it is advantageous that the reflected light with the larger converging angles could be collected and then guided into the optical components of the projector. However, the optical thin film performance is related to the incidence angle of light. The larger the incidence angle of light is, the poorer the optical performance is. For example, when the reflected light with an undesired shifted optical spectrum is produced, then an inaccuracy in color of images illuminated by the reflected light or deterioration in contrast of the same images is disadvantageously occurred.
In view of the above, it is required a structure capable of reducing the converging angle of the reflected light and collecting all of the light emitted from the light source, so that it is possible to improve the corresponding illumination efficiency and simultaneously preserve the desired accuracy in color and contrast.
Thus, it is an object of the present invention to provide a structure for reflection of light capable of reducing the converging angle of the reflected light so as to improve the corresponding illumination efficiency and simultaneously preserve the desired accuracy in color and contrast.
It is another object of the present invention to provide a structure for collecting light capable of condensing the respective light emitted from two light sources on an area of a spot size and still retaining the converging angle as the same as that of the conventional structure so as to achieve an effect on more brightness and uniformity.
The structure for reflection of light is provided according to one embodiment of the present invention, which comprises a curved surface reflector for reflecting the light emitted from a light source located on a first focus of the curved surface reflector, and a semi-sphere surface reflector for reflecting the light emitted from the light source located on a center of the semi-sphere surface, wherein the first focus of the curved surface reflector and the center of the semi-sphere surface are so positioned as to be substantially on the same location. Thus, after the light emitted from the light source, half of the light beam will illuminate on the semi-sphere surface reflector and is reflected by the semi-sphere surface reflector. The reflected light will passes through the center of the semi-sphere surface again to illuminate on the curved surface reflector. The other half of light beam will illuminate on the curved surface reflector directly, so that all of the light reflected by the semi-sphere surface can pass through the center to illuminate on the curved surface reflector and is then reflected by the same.
It is preferred that the curved surface reflector is a semi-ellipsoid, so that the light reflected by the reflector is condensed at a second focus of the semi-ellipsoid.
It is preferred that the curved surface reflector is a semi-paraboloid. In this case, the structure further comprises a lens for condensing the light reflected by the reflector at a second focus.
A structure for collecting light is provided according to another embodiment of the present invention, which comprises a first curved surface reflector for reflecting the light emitted from a first light source located on a first focus of the first curved surface reflector, a second curved surface reflector for reflecting the light emitted from a second light source located on a first focus point of the second curved surface reflector, a first semi-sphere surface reflector for reflecting the light emitted from the first light source located on a center of the first semi-sphere surface, and a second semi-sphere surface reflector for reflecting the light emitted from the second light source located on a center of the second semi-sphere surface, wherein the first focus of the first curved surface reflector and the center of the first semi-sphere surfaces are so positioned as to be substantially on a first location, the first focus of the second curved surface reflector and the center of the second semi-sphere surfaces are so positioned as to be substantially on a second location, and after the light emitted from the first and second light sources is reflected by the first and second semi-sphere surfaces, respectively, the reflected light pass through the respective centers of the semi-sphere surfaces to illuminate on the first and second curved surface reflectors, respectively, so that all of the light reflected by the first and second semi-sphere surfaces can pass through the respective centers to illuminate on the respective curved surface reflector, be reflected by the same, then be condensed at a second focus.
It is preferred that a combination of the first curved surface reflector and the first semi-sphere surface reflector and another combination of the second curved surface reflector and the second semi-sphere surface reflector are arranged in an angular manner.
It is preferred that the curved surface reflector is a semi-ellipsoid, so that the light reflected by the structure is condensed at a second focus of the semi-ellipsoid.
It is preferred that the curved surface reflector is a semi-paraboloid. In this case, the structure further comprises a lens for condensing the light reflected by the structure at a second focus.